The invention disclosed and claimed herein generally pertains to a crank bait fishing lure which may be readily set or adjusted to operate at a number of different depth levels. More particularly, the invention pertains to a crank bait lure having a depth adjustment mechanism, wherein principal components thereof are protectably housed or contained within the interior of the lure. Even more particularly, the invention pertains to a crank bait lure of the above type which is comparatively simple and inexpensive to manufacture.
As is well known by those of skill in the art, a crank bait fishing lure is a type of artificial lure which is cast or otherwise placed into a body of water containing game fish. A line attached to the lure is then wound upon a reel or the like, by turning or cranking the reel, so that the lure is drawn through the water. In such arrangements, it is very common to attach the line to the forward end, or nose of the lure, and also to provide a member, variously referred to as a lip, a spoon, or a bill, which extends in front of the nose. As the lure is being drawn through the water, the combination of forces applied to the lure, by the line and by the lip member acting against the water, causes the lure to dive. The angle at which the lure dives, or diving angle, is determined by the shape and length of the extending lip member.
It has long been recognized that there are significant advantages in mounting the lip or bill so that the length of the lip portion extending in front of the lure can be selectively changed or adjusted. Generally, increasing the length of such extending portion increases diving angle, so that the lure travels to a greater depth as it moves through the water. Conversely, reducing the length of the extending lip portion reduces diving angle, so that the lure remains closer to the surface as it moves. Thus, a single lure may be configured to operate at different levels, to accommodate different conditions and to be used for different types of fish.
U.S. Pat. No. 4,215,507, issued Aug. 5, 1980 to Russell, exemplifies a class of fishing lures which are provided with an adjustable bill member or the like. As shown thereby, it is conventional practice to secure the adjustable member in place, with respect to the lure body, by means of a screw or the like. However, while a screw may be effective initially for such purpose, over time and after repeated use, the threads in the lure body engaged by the screw may tend to wear. As this occurs, it becomes increasingly difficult for the screw to provide sufficient holding force to prevent slippage of the bill member. As a result, the diving angle, and therefore the depth reached by the lure, could change unexpectedly and at an inopportune time, such as just after the lure has been cast. Moreover, wear of the lure body threads may be accelerated if plastics or other new materials are substituted for wood, which has previously been the material of choice for fishing lures.
The arrangement shown by the Russell patent illustrates a further disadvantage in certain lures of the prior art. As is well known, a fishing lure can be subjected to substantial stresses, such as when a fish takes a lure hook or the lure becomes snagged on underwater debris. In the arrangement of Russell, the line attachment point is mounted on the adjustable bill. Accordingly, most of the stresses applied to the lure, by action of the attached line and hooks, are directed right through the the bill member retention screw, and through the threads engaged thereby. Such stresses will tend to hasten the wear of the threads, further degrading the holding power of the retention screw.